Question about in-line venting and room size

I am just in the process of designing my medical grow space, and was wondering if I could get some advice about vents.

At this point, I have two options, a tent or a room. I will be using a 400w HPS, with four plants.
I was planing on ducting an inline fan hooked up to a carbon filter to my rooftop, but i had a question about the effect of the room vs tent SIZE on ventilation needs.

The room is about XXXXX,
However, a tent I had my eye on is about 40*40*79 (is that big enough for four SOG plants?)

The question is, despite both options having only a 400W HPS and 4 plants, the actual SIZE of the spaces will be vastly different. Will I need additional in-line ventilation due to the room being bigger DESPITE the same heat and smell problem. Lastly, will this affect light distribution? what are your recommendations?

I plan on using a floor fan on top of the inline fan.

Thank you so much for your help guys.

Sorry about the XXXX ... the room is about 12 feet*8 feet*8 feet

What's up, jazzman? I am a newbie myself but I will try to give my opinion based on my experience. I am currently growing in a 12x8 room with 2-1000w hps lights. I hooked up a 360cfm inline fan just because I came across it at a great deal. To my surprise, it does a great job with the smell. However, it doesn't do much for heat. I have a window ac unit in the room that takes care of that. I can't imagine why you wouldn't be able to vent the ac unit into the grow tent. As far as light distribution, it will make a difference with the space you use. However, in the large open room, all you'd really have to do is line a corner of the room with Mylar or panda film and then find the most convenient way to hang it around te other side of the plants, maybe even erect little walls or make a frame using PVC, you'll want something you can easily move or duck under to get to the plants. Your question is kind of vague and is really a matter of how much work and money you want to put into this. Also, you really have to see what happens once you start. Depending on the weather where you are, you might not need an ac unit for a 400w light, especially in a large room with good air circulation. Either way, I hope this helps! Good luck man.

Hey! Really appreciate the advice, glad to know about the smell and the light. The weather is SoCal so never that hot nor very cold. The AC unit would be an acceptable solution, but how much do small AC units usually run on a good day? Do you have one of those lamps with a venting hood? I've heard good things about them but wondering if its really enough in the end. I'm willing to put a lot of work into it but money is more limited. Thanks for the advice Drumfounded!

Jazzman Rice said:

Hey! Really appreciate the advice, glad to know about the smell and the light. The weather is SoCal so never that hot nor very cold. The AC unit would be an acceptable solution, but how much do small AC units usually run on a good day? Do you have one of those lamps with a venting hood? I've heard good things about them but wondering if its really enough in the end. I'm willing to put a lot of work into it but money is more limited. Thanks for the advice Drumfounded!

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My ac unit never shuts off, lol. I got really lucky in that I leave it on the highest setting and keep it on 24/7 and my daytime temps along with nighttime temps are exactly where I want them. I do have vented goods but because my fan is way underrated for the room I'm in, I don't actively vent the hoods. With a 400w, I feel like a vented hood is unnecessary, especially if you have the fund for an ac unit. Like I said, I'm running two 1000w lights, along with their extremely warm magnetic ballasts. My dehumidifier also puts out a good deal of heat and I control it all with the ac unit.

Just realize after posting that for money purposes, you may want to go with a vented hood instead of the ac unit. I believe with running a 400w light, that a decent fan should adequately vent the heat. Again, I am a newbie myself so please don't take my opinions as facts!

I gotcha. Would you think is 400w enough for 4 OGs in SOG? Cuz your setup is crazy man! haha
Is there a convenient way to duct the lighting heat directly to an in-line fan?

and sorry I meant how much will they run you aka price haha my bad

Also I might ask, does your light fixture have the ballast inside it or is it separate?

Jazzman, yes, it is pretty easy to vent hoods with an inline fan. It's incredibly simple. Once you find the fan to fit your space and the light hood of your choice, just connect the two with ducting! To make it super convenient, but a hood and fan with the same circumference. A 4" hood connected with 4" ducting to a 4" fan or a 6" hood connected with 6" ducting to a 6" fan. The only thing that wouldn't be completely idiot proof is if the hood vents are a different size than the fan. Even then, all you would need is a reducer which is pretty common and cheap. As far as the price of my ac unit, I couldn't tell you man. Wish I could be more help but I'm not a very efficient grower and don't look at my bill too often, lol. Look up how much your electric company charges you, usually it's by the kilowatt per hour. Then figure out how many watts your equipment draws. For instance, my two 1k light = 2 kilowatts per hour. Multiply 2 by the price you pay per hour, then multiply that figure by how many hours a day the equipment is running. My lights have seperate ballast from the hood and socket. To be honest, I don't think I have ever seen a grow light that is attached to the ballast other that by the power supply cable. Hope I'm helping you get a little closer to growing man!

And to answer your question on whether 400w is enough, I think so. Obviously, the more light you have the better. With that being said, I've seen some good looking nugs grown from much less light. It really depends on how big you want the plants and how much you'd like to pull from them. Definitely do your homework on topping, FIMing, lollypopping, pruning and Scrog growing. Figure out which one might best suite your goals and give it a try. I wouldn't be concerned with 400w on 4 plants unless you want the plants to be huge, in which case, I would definitely try a Scrog grow so all your buds can soak up that sun!

Yup! This is all real useful, I think maybe I will just go with the inline fan running into the lamp and a desktop fan. Does this mean that the vent will be less effective in carrying smell? How are your vents placed to capture smell?
I will run the lights for a bit and see how hot they get with the fans, and adjust accordingly.

Alright that's great, we're looking at easy clones like Big Bud, Afghan Kush, Kushberry, and Romulan. I hear they are rather forgiving. Any advice on how to care for the clones (they are already well rooted) in their early years of soil? Do they need more water or less light?

And SCROG looks awesome. I will definitely do my homework before proceeding haha

Also, look up lst. Perhaps might be the simplest way to expose your plants to more light without too much stress to the plant. Treat them like you would a woman. The first time around, it's best to play it safe, just let them do they're thing. Be observant and learn from them. Once you get comfortable, get a little rough! Experiment with some more advanced techniques. Just go little by little and pay attention to how they respond to the stress.

Well you're eventually gonna want to get a carbon filter. Any air being vented from the grow room with keep the humidity and smell down, while in veg. Once you get to flowering, you're definitely going to want to get a carbon filter. You don't necessarily need it to pull the smell from the room, but you don't want that pungent smell floating around into your neighbors windows! How old are the clones? You're growing in soil? They do 'require' less light but a 400w won't burn em'. Just make sure you keep it at a good distance. People say use your hand to make sure it is not too warm but that's mostly with more mature plants. For newly rooted clones, I would say keep it at least two feet away, if not a little further.

haha that's hilarious ! and a perfect metaphor ...

I'll be buying clones from a grower, and yeah I was planning to use a soil composite. Is this not optimal?
LST looks like a great idea. I don't understand how SCROG's results differ from those of LST, though I see the difference in method.

Anyway, you've given me a lot to think about, I really appreciate it, I'll keep you updated

Not knocking the soil at all man, just making sure I knew what your medium was. I scrog myself and have never lst'd so I can't be completely confident when I say this...
I believe the results should be similar. With the lst, the goal is to get more light to the smaller 'popcorn' bud sites, thus turning them into denser, more desirable buds. With scrog, most growers remove all the lower growth as almost zero light can penetrate the canopy of a scrog. However, with all that undergrowth being removed, the plant will focus all it's energy into the top colas, producing larger top sites than if you just let te plant grow. It seems to me, that if done properly, either method should yeild good results as far as quality and weight. Is one better than the other? I really couldn't tell you dude. They are both great ways to maximize the use of your lights and also, if done right, they are both great ways to keep plants in a grow space that is limited on height. Definitely keep me updated man, id love to see which methods you choose and how it turns out for ya!

Having not read all the replies (sorry if I duplicate anything), what I would do is divide your room in two. Just using half for now, but later you can veg on one side and flower on the other. With this new smaller room I would put a 4x10 filtered passive vent intake (4x10 whole in the wall by the floor with some filter material over it, if your running on the cheap.) I would then run a vented hood which would intake from the room and via negative pressure, now suction of fresh air will all be filtered through your 4x10 vent. So now you are venting your hood and exchanging room air with only one fan. Next I would run 4 inch flex duct from my hood to a 200cfm online Fan outside my room. The attic is a possibility if tying into your dryer vent is not an option. On the exhaust side of the fan I would place my carbon filter, inside out style. Just remember to pre filter from the inside of you carbon filter now. (Not all carbon filters can be run inside out so check with your manufacturer.) As far as temp control as long as your ambient temp outside the room never gets above 75f, or below 50f you should have no problem controlling the temperature with a fan speed controller alone.